Blades, U.S. Pat. No. 3,767,756, describes the spinning of anisotropic acid solutions of aromatic polyamides into a noncoagulating fluid, for example, air, and then into a coagulating liquid, for example, water.
Yang, U.S. Pat. No. 4,340,559, describes an improved process over that disclosed in Blades. In Yang, the anisotropic spinning solution is passed through a layer of noncoagulating fluid and into a shallow bath of coagulating (and quenching) liquid and out through an orifice at the bottom of the bath. The flow in the bath and through the outlet orifice is nonturbulent. In Yang, some of the filaments (i.e., extruded solution) contact the coagulating bath at a different angle than other filaments do. In Yang, the path of the filaments (extruded solution) through the noncoagulating fluid varies in length from one filament to another. In Yang, the filaments that are extruded from the circle of apertures closer to the center of the spinneret are contacted by coagulating fluid that has a somewhat different composition than the liquid that contacts the filaments that are formed at spinneret apertures at the outer edge of the spinneret--due of course to the coagulating liquid having become "contaminated" with the sulfuric acid leached from the fibers situated near the perimeter.